Andy Lopez was walking to his friend’s house in Santa Rosa, Calif. on Oct. 22 when two Sonoma County deputies spotted the 13-year-old boy in a blue hoodie carrying what they thought was an AK-47 assault rifle. Stopping the police car, the deputies chirped their siren and demanded that he drop the gun. Still holding it, Lopez started to turn around. A deputy, believing he was in danger, fired several rounds. Lopez was shot seven times and died on the scene. What the officers took for an assault rifle turned out to have been an airsoft gun that fires plastic projectiles.

Santa Rosa has been rocked by the event, with hundreds marching on Wednesday to protest the shooting of “an innocent young boy,” as one sign read. The deputies, who have not been named, are on leave while the incident is investigated, and the FBI announced on Saturday that they’re conducting an independent investigation of the incident.

The shooting is the latest in a long line of incidents of police shooting — and sometimes killing — people whom they have mistakenly thought to be armed with a real firearm. Last year, police fatally shot a Texas eighth-grader who was carrying a pellet gun that resembled a black Glock. The year before, Miami police shot and killed a 57-year old man who had a realistic replica gun after getting 911 calls about the ostensible weapon. “This is not the first time,” says Karen Caves, spokeswoman for a California state senator who has pushed stricter regulations on imitation firearms. “It happens every year.”

The Department of Justice says the federal government doesn’t keep ongoing statistics on the trend, but in a 1990 paper funded by the Bureau of Justice Statistics, U.S. police reported that they had used or threatened to use force “in a confrontation where an imitation gun had been mistaken for a real firearm” at a rate of about 200 incidents per year. The paper’s authors suggested that this number was “significantly underreported.” A series of toy gun-related deaths in the late 80s helped pass a federal amendment, sponsored by Republican Sen. Bob Dole, that requires all toy, “look-alike,” or imitation firearms to have a bright orange plug or other salient marking. But manufacturers don’t always adhere to required standards and markings can be altered, according to law enforcement.

In a press conference on Wednesday, Santa Rosa police investigating the incident emphasized that Lopez’ airsoft gun did not have the required orange marker and public information officer Paul Henry says that the front portion had been removed. Unzipping two cases, an officer showed reporters a real AK 47-style rifle and the imitation that the teenager was carrying. “The firearm and airsoft rifle appeared remarkably similar, with matching black banana clips and brown stocks,” wrote the Santa Rosa Press Democrat. “Yet in the light of the [building where the conference was held] the model Lopez carried was clearly plastic with a transparent center section.” (In some places, restrictions on imitation guns require them to be made entirely of transparent materials.)

Law enforcement veterans who have made similar split-second decisions caution that police have to react instantly to potential threats. Jim Yurgealitis, a former agent for the Bureau of Alcohol, Firearms, Tobacco and Explosives, worked the streets of Baltimore for more than a decade. He says the first time he ever found himself in a “shoot, don’t shoot situation” was when he and other officers mistook a BB gun that resembled a Colt .45; luckily, the man holding it handed it over and no shots were fired.

“In a stressful situation where it’s a question of using deadly force, you are not going to be able to get close enough to give a detailed inspection,” Yurgealitis says. “Officers have to make a decision in milliseconds and everybody can second guess it.” The deputies in Santa Rosa were roughly 20 to 30 feet from Lopez during the incident.

Some states and cities have passed legislation that goes beyond the federal requirement, whether banning toy guns that look realistic or requiring that certain replica guns not be sold to minors. In 2003, members of the New York City Council attempted to ban toy guns entirely. And in 2011, California State. Sen. Kevin de Leon pushed legislation that would have required the exterior surface of BB guns, which federal law does not require to be marked with blaze orange, to be brightly colored—a change meant to make them harder to mistake for real firearms. Because of a push by gun rights advocates in the state, his communications director Caves says, the bill had to be narrowed until it affected only the County of Los Angeles.

“These guns don’t belong on the street,” says Caves. “They endanger children and they endanger police … You can simply paint them some bright fluorescent colors that will give police an opportunity to easily identify them for what they really are and avoid this type of tragedy.” The Center for Public Integrity reports that critics of de Leon’s bill argued that real guns are now being painted bright colors too, which could lead to fatal confusion for officers, and that alternative colors could incorrectly suggest that BB guns are entirely safe and never lethal.

Governments elsewhere in the U.S. have been dealing with toy guns. A New Jersey bill currently in committee, for instance, would make it a crime to mask or color the orange tip of a toy gun (as well as to disguise a real gun with such markings). And in August, after police in Carrollton, Texas, were alerted that students were carrying “facsimile firearms” on school property, the city council banned the carrying of fake guns wherever real ones are prohibited. “We aren’t talking about neon green water guns,” the police chief told a local paper. “These guns are modeled after the real firearms … Without close inspection you can hardly tell them apart.”